Structural Analysis of Peptides of PSⅡ Light-harvesting Complexes in Siphonous Green Algae, Codium fragile

Peptide composition and arrangement of 4 major light-harvesting complexes LHCP 1-3 and LHCP 3′ isolated from siphonous green algae (Codium fragile (Sur.) Hariot.) were investigated. LHCP 1 showed five main peptides, 34.4, 31.5, 29.5, 28.2 and 26.5 kD in SDS-PAGE, the 34.4 and 31.5 kD peptides were never found in higher plants. LHCP 3 contained the other four kinds of LHCP 1 peptides except 34.4 kD, while LHCP 3′ consisted of only 28.2 and 26.5 kD peptides. We found that 34.4, 28.2 and 26.5 kD peptides were easy to decompose from LHCP 1 when subjected to SDS-PAGE without pretreatment. They might be located at the exterior of LHCP 1, while the 31.5 and 29.5 kD peptides were at the central part. The 28.2 and 26.5 kD peptides often occurred in CPa, the center complex of PSⅡ. They are possibly the LHCⅡ peptides tightly associated with CCⅡ. According to the results described above, a peptide map of LHCP 1 was sketched.

Long-Lived Coherence Originating from Electronic-Vibrational Couplings in Light-Harvesting Complexes

We theoretically investigate the evolutions of two-dimensional, third-order, nonlinear photon echo rephasing spectra with population time by using an exact numerical path integral method. It is shown that for the same system, the coherence time and relaxation time of excitonic states are short, however, if the couplings of electronic and intra-pigment vibrational modes are considered, the coherence time and relaxation time of this vibronic states are greatly extended. It means that the couplings between electronic and vibrational modes play important roles in keeping long-lived coherence in light-harvesting complexes. Particularly, by using the method we can fix the transition path of the energy transfer in bio-molecular systems.

Identification of Light-Harvesting Chlorophyll a/b-Binding Protein Genes of Zostera marina L.and Their Expression Under Different Environmental Conditions

Photosynthesis includes the collection of light and a/b-binding （LHC） proteins. In high plants, the LHC gene family constituting the light-harvesting complex ofphotosystems I and II. the transfer of solar energy using light-harvesting chlorophyll includes LHCA and LHCB sub-families, which encode proteins Zostera marina L. is a monocotyledonous angiosperm and inhab- its submerged marine environments rather than land environments. We characterized the Lhca and Lhcb gene families of Z. marina from the expressed sequence tags （EST） database. In total, 13 unigenes were annotated as ZmLhc, 6 in Lhca family and 7 in ZmLhcb family. ZmLHCA and ZmLHCB contained the conservative LHC motifs and amino acid residues binding chlorophyll. The average similarity among mature ZmLHCA and ZmLHCB was 48.91% and 48.66%, respectively, which indicated a high degree of diver- gence within ZmLHChc gene family. The reconstructed phylogenetic tree showed that the tree topology and phylogenetic relation- ship were similar to those reported in other high plants, suggesting that the Lhc genes were highly conservative and the classification of ZmLhc genes was consistent with the evolutionary position of Z. marina. Real-time reverse transcription （RT） PCR analysis showed that different members of ZmLhca and ZmLhcb responded to a stress in different expression patterns. Salinity, temperature, light intensity and light quality may affect the expression of most ZmLhca and ZmLhcb genes. Inorganic carbon concentration and acidity had no obvious effect on ZmLhca and ZmLhcb gene expression, except for ZmLhca6.

Incorporating porphyrin-Pt in light-harvesting metal-organic frameworks for enhanced visible light-driven hydrogen production

Molecular catalysts for H2-evolution are of interest for their integration into light-harvesting complexes for photocatalytic water splitting.Here,we report the meso-tetra(4-carboxyphenyl)porphine[(TCPP)Pt^(Ⅱ)]complex as a molecular H2-evolving photocatalyst using chloranilic acid(CA)as a sacrificial electron donor,the choice of which is critical to the stability of the photocatalyst.When triethanolamine was used,[(TCPP)Pt^(Ⅱ)]decomposed to form Pt nanoparticles.Density functional theory calculations together with evidence from electrochemical and spectroscopic analyses suggested that the catalysis was possibly initiated by a proton-coupled electron transfer(PCET)to form[(TCPP)Pt^(Ⅰ)]-N-H,followed by another electron injection and protonation to form a[(TCPP)Pt^(Ⅱ)-hydride]-N-H intermediate that can release H2.As the whole catalytic cycle involves the injection of multiple electrons,a light-harvesting network should be helpful by providing multiple photo-induced electrons.Thus,we integrated this molecular catalyst into a light-harvesting metal-organic framework to boost its activity by~830 times.This work presents a mechanistic study of the photocatalytic H2 evolution and energy transfer and highlights the importance of a light-harvesting network for multiple electron injections.

Self-assembly of biomimetic light-harvesting complexes capable of hydrogen evolution

Biomimetics provides us a new perspective to understand complex biological process and strategy to fabricate functional materials. However,a great challenge still remains to design and fabricate biomimetic materials using a facile but effective method. Here, we develop a biomimetic light harvesting architecture based on one-step co-assembly of amphiphilic amino acid and porphyrin. Amphiphilic amino acid can self-assemble into nanofibers via π-stacking and hydrogen binding interactions. Negatively charged porphyrin adsorbs on the surface of the assembled nanofibers through electrostatic force, and the nanofibers further organize into porous urchin-like microspheres induced presumably by hydrophobic interaction. The assembled amphiphilic amino acid nanofibers work as a template to tune the organization of porphyrin with an architecture principle analogous to natural light harvesting complex. The co-assembled microspheres exhibit enhanced light capture due to the light reflection in the porous structure. Reaction center(platinum nanoparticles) can be effectively coupled with the light harvesting microspheres via photoreduction. After visible light illumination, hydrogen evolution occurs on the hybrid microspheres.

Characteristics and phylogeny of light-harvesting complex gene encoded proteins from marine red alga Griffithsia japonica

Six genes encoding light-harvesting complex (LHC) protein have been characterized in the multicellular red alga Griffithsia japonica EST analysis. Three of them were full sequences while others were partial sequences with 3'-UTRs. The cleavage sites between signal peptide and mature LHC protein were analyzed on these three full sequences. The sequence characteristics, calculated molecular weights and isoelectric point (pI) values and hydrophobicity of the mature proteins were deduced and analyzed. Comparing the LHC sequences of G. japonica with higher plant, Chlorophyta, chromophytes and other red algae, the high conservation of the chlorophyll (Chl) binding site among chromophytes and red algae were revealed. Phylogenetic analysis on LHC proteins from higher plant, green algae, euglena, brown algae, diatom, cryptomonad, Raphidophyte and red algae reveals that (1) there are two distinct groups of Chl a/b and Chl a/c -binding LHC; (2) Chl a binding proteins of red algae share greater similarities with the Chl a/c-binding proteins of the chromophytes and dinoflagellate than with the Chl a/b - binding proteins of the green algae and higher plants; (3) chromophyte's LHC is supposed to be evolved from red algae LHC.

Energy transfer between two aggregates in light-harvesting complexes

Energy transfer processes between two aggregates in a coupled chromophoric-pigment （protein） system are studied via the standard master equation approach. Each pigment of the two aggregates is modeled as a two-level system. The excitation energy is assumed to be transferred from the donor aggregate to the acceptor aggregate. The model can be used to theoretically simulate many aspects of light-harvesting complexes （LHCs）. By applying the real bio-parameters of photosynthesis, we numerically investigate the efficiency of energy transfer （EET） between the two aggregates in terms of some factors, e.g., the initial coherence of the donor aggregate, the coupling strengthes between the two aggregates and between different pigments, and the effects of noise from the environment. Our results provide evidence for that the actual numbers of pigments in the chromophoric tings of LHCs should be the optimum parameters for a high EET. We also give a detailed analysis of the effects of noise on the EET.

Theoretical study on the exciton dynamics of coherent excitation energy transfer in the phycoerythrin 545 light-harvesting complex

The experimental observation of long-lived quantum coherence in the excitation energy transfer(EET)process of the several photosynthetic light-harvesting complexes at low and room temperatures has aroused hot debate.It challenges the common perception in the field of complicated pigment molecular systems and evokes considerable theoretical efforts to seek reasonable explanations.In this work,we investigate the coherent exciton dynamics of the phycoerythrin 545(PE545)complex.We use the dissipation equation of motion to theoretically investigate the effect of the local pigment vibrations on the population transfer process.The result indicates that the realistic local pigment vibrations do assist the energy transmission.We demonstrate the coherence between different pigment molecules in the PE545 system is an essential ingredient in the EET process among various sites.The coherence makes the excitation energy delocalized,which leads to the redistribution of the excitation among all the chromophores in the steady state.Furthermore,we investigate the effects of the complex high-frequency spectral density function on the exciton dynamics and find that the high-frequency Brownian oscillator model contributes most to the exciton dynamic process.The discussions on the local pigment vibrations of the Brownian oscillator model suggest that the local heterogeneous protein environments and the effects of active vibration modes play a significant role in coherent energy transport.

Azobenzene-based ultrathin peptoid nanoribbons for the potential on highly efficient artificial light-harvesting

The development of artificial light-harvesting systems based on long-range ordered ultrathin organic nanomaterials(i.e., below3 nm), which were assembled from stimuli-responsive sequence-controlled biomimetic polymers, remains challenging. Herein,we report the self-assembly of azobenzene-containing amphiphilic ternary alternating peptoids to construct photo-responsive ultrathin peptoids nanoribbons(UTPNRs) with a thickness of ~2.3 nm and the length in several micrometers. The pendants hydrophobic conjugate stacking mechanism explained the formation of one-dimensional ultrathin nanostructures, whose thickness was highly dependent on the length of side groups. The photo-isomerization of azobenzene moiety endowed the aggregates with a reversible morphology transformation from UTPNRs to spherical micelles(46.5 nm), upon the alternative irradiation with ultraviolet and visible light. Donor of 4-(2-hydroxyethylamino)-7-nitro-2,1,3-benzoxadiazole(NBD) and acceptor of rhodamine B(RB) were introduced onto the hydrophobic and hydrophilic regions, respectively, to generate photocontrollable artificial light-harvesting systems. Compared with the spheres-based systems, the obtained NBD-UTPNRs@RB composite proved a higher energy transfer efficiency(90.6%) and a lower requirement of RB acceptors in water. A proof-ofconcept use as fluorescent writable ink demonstrated the potential of UTPNRs on information encryption.

Assembly of highly efficient aqueous light-harvesting system from sequence-defined peptoids for cytosolic microRNA detection

Precisely controlled spatial distributions of artificial light-harvesting systems in aqueous media are of significant importance for mimicking natural light-harvesting systems;however,they are often restrained by the solubility and the aggregation-caused quenching effect of the hydrophobic chromophores.Herein,we report one highly efficient artificial light-harvesting system based on peptoid nanotubes that mimic the hierarchical cylindrical structure of natural systems.The high crystallinity of these nanotubes enabled the organization of arrays of donor chromophores with precisely controlled spatial distributions,favoring an efficient Förster resonance energy transfer(FRET)process in aqueous media.This FRET system exhibits an extremely high efficiency of 98.6%with a fluorescence quantum yield of 40%and an antenna effect of 29.9.We further demonstrated the use of this artificial light-harvesting system for quantifying miR-210 within cancer cells.The fluorescence intensity ratio of donor to acceptor is linearly related to the concentration of intercellular miR-210 in the range of 3.3–156 copies/cell.Such high sensitivity in intracellular detection of miR-210 using this artificial light-harvesting system offers a great opportunity and pathways for biological imaging and detection,and for the further creation of microRNA(miRNA)toolbox for quantitative epigenetics and personalized medicine.

Carbon dot-based artificial light-harvesting systems with sequential energy transfer and white light emission for photocatalysis

In this work, we designed and synthesized cationic carbon dots(CDs) with a size distribution of 1.6–3.7 nm, which exhibited dark blue fluorescence in the aqueous solution. Based on its excellent luminescence properties, we used it as an energy donor to construct a sequential artificial light-harvesting system(LHS) by employing the energy-matching dyes eosin Y disodium salt(EY) and sulforhodamine101(SR101), which could regulate the white light emission(Commission Internationale de l'Eclairage(CIE) coordinate:(0.30, 0.31)) with the energy transfer efficiency(ΦET) of 53.9% and 20.0%. Moreover, a single-step artificial LHS with white light emission(0.32, 0.28) can be constructed directly using CDs and dye solvent 43(SR) with ΦETand antenna effect(AE) of 48.8% and 6.5, respectively. More importantly,CDs-based artificial LHSs were firstly used in photocatalytic of α-bromoacetophenone, with a yield of90%. This work not only provides a new strategy for constructing CDs-based LHSs, but also opens up a new application for further applying the energy harvested in CDs-based LHSs to the field of the aqueous solution photocatalysis.

Recent advances in two-step energy transfer light-harvesting systems driven by non-covalent self-assembly

Sequential energy transfer is ubiquitous in natural light-harvesting systems(LHSs),which greatly promotes the exploitation of light energy.The LHSs in nature are sophisticated supramolecular assemblies of chlorophyll molecules that carry out efficient light harvesting through cascade energy transfer process.Inspired by nature,scientists have paid much attention to fabricate stepwise LHSs based on assorted supramolecular scaffolds in recent years.Light-harvesting antennas and energy acceptors can be accommodated in particular scaffolds,which offer great convenience for energy transfer between them.These systems not only further mimic photosynthesis,but also demonstrate many potential applications,such as photocatalysis,tunable luminescence,and information encryption,etc.In this review article,aiming at offering a practical guide to this emerging research field,the introduction of construction strategies towards sequential LHSs will be presented.Different scaffolds are classified and highlighted,including host-guest assemblies,metal-coordination assemblies,as well as bio-macromolecular and other supramolecular scaffolds.

Pillar[5]arene based artificial light-harvesting supramolecular polymer for efficient and recyclable photocatalytic applications

Photosynthesis is the process through which living plants utilize photosynthetic pigments,such as chlorophyll,to convert CO_(2)and water into organic compounds and release O_(2)under visible light.In this study,we have successfully constructed a fluorescent supramolecular polymer(P5Py_(2)/Zn/Gen)n by employing orthogonal pillar[5]arene-based molecular recognition and metal ion coordination.Within the supramolecular polymer,the guest molecule Gen unit acts as a light-harvesting moiety,as the ACQ effect is inhibited by host-guest interactions,while the(Py)_(2)/Zn center serves as a catalytic site.By employing this orthogonal self-assembly strategy,we have enhanced the stability of both the donor and acceptor in catalyzing the reduction of p-nitrophenol to p-aminophenol.Moreover,this photocatalyst can be reused at least 5 times without significant conversion loss.These findings provide a pathway for constructing a recyclable artificial LHS that mimics the entire photosynthesis process.

Assembling aggregation-induced emission with natural DNA to maximize donor/acceptor ratio for efficient light-harvesting antennae

Arranging dense donors around a single acceptor for the assembly of effi-cient light-harvesting antennas is a long-standing challenge due to the intractable aggregation-caused quenching of dense donors.Herein,we designed a cationic aggregation-induced emission(AIE)amphiphile to self-assemble with natural DNA duplexes.As an efficient donor,the as-prepared cationic AIE amphiphile could be densely attached to the phosphate groups of natural DNA duplexes by using the smaller cationic trimethylammonium.The long alkyl chain between the cationic trimethylammonium and the AIEfluorophore allowed for avoiding the insuffi-cient binding caused by the steric hindrance of the AIEfluorophore,resulting in a remarkably high donor/acceptor ratio comparable to that of the widely developed custom DNA assemblies.The proposed self-assembly strategy provided novelflex-ible avenues for the assembling offinely controlled and efficient light-harvesting systems into natural DNA with little synthetic modifications and low cost.

Construction and application of the polyelectrolyte-based sequential artificial light-harvesting system

In this work,we have designed and synthesized a cyano-substituted p-phenylenevinylene derivative(PPTA),which can self-assemble into positively charged nanoparticles in an aqueous solution with a deep green fluorescence.An anionic polyelectrolyte material guar gum modified by carboxylic acid(GP5A)was chosen to build an artificial light-harvesting system(LHS)through self-assembly with PPTA,in which two acceptors Eosin Y(EY)and Nile red(NiR)were loaded into the PPTA-GP5A assemblies through electrostatic interaction and Van der Waals force.By adjusting the molar ratio of PPTA-GP5A/EY at 1:0.004,the one-step artificial LHS can exhibit high energy transfer efficiency(Φ_(ET))(38.9%)and antenna effect(AE)(4.6).Subsequently,with the addition of NiR,theΦET and AE of the two-step sequential artificial LHS were calculated to be 71.9%and 13.5,respectively.Moreover,the two-step artificial LHS constructed by the polyelectrolyte material GP5A can be used as a nanoreactor to photocatalyst alkylation of C-H bonds of phenyl vinyl sulfone(PVS)and tetrahydrofuran(THF)in water with a yield of 42%.Therefore,we have constructed an artificial LHS with two-step energy transfer based on polyelectrolytes through the electrostatic interaction to improve energy transfer efficiency,which can also be used as a nanoreactor for photocatalysis.

Boosting the efficiency of quantum dot–sensitized solar cells over 15%through light-harvesting enhancement

How to improve the capacity of light-harvesting is still an important point and essential strategy for the assembling of high-efficiency quantum dot–sensitized solar cells(QDSCs).A believable approach is to implant new light absorption materials into QDSCs to stimulate the charge transfer.Herein,the few-layer black phosphorus quantum dots(BPQDs)are synthesized by electrochemical intercalation technology using bulk BP as source.Then the obtained BPQDs are deposited onto the surface of Zn–Cu–In–S–Se(ZCISSe)QD-sensitized TiO2 substrate to serve as another light-harvesting material for the first time.The experimental results have shown that BPQDs can not only increase the absorption intensity by photoanode but also reduce unnecessary charge recombination processes at the interface of photoanode/electrolyte.Through optimizing the size and deposition process of BPQDs,the champion power conversion efficiency of ZCISSe QDSCs is increased to 15.66%(26.88 mA/cm2,Voc=0.816 V,fill factor[FF]=0.714)when compared with the original value of 14.11%(Jsc=25.41 mA/cm^(2),Voc=0.779 V,FF=0.713).

Novel Evidence for a Reversible Dissociation of Light-harvesting Complex II from Photosystem II Reaction Center Complex Induced by Saturating Light Illumination in Soybean Leaves

After saturating light illumination for 3 h the potential photochemical efficiency of photosystem Ⅱ （PSII） （FJF,, the ratio of variable to maximal fluorescence） decreased markedly and recovered basically to the level before saturating light illumination after dark recovery for 3 h in both soybean and wheat leaves, indicating that the decline in FJ/Fm is a reversible down-regulation. Also, the saturating light illumination led to significant decreases in the low temperature （77 K） chlorophyll fluorescence parameters F685 （chlorophyll a fluorescence peaked at 685 nm） and F685/F735 （F735, chlorophyll a fluorescence peaked at 735 nm） in soybean leaves but not in wheat leaves. Moreover, trypsin （a protease） treatment resulted in a remarkable decrease in the amounts of PsbS protein （a nuclear gene psbS-encoded 22 kDa protein） in the thylakoids from saturating light-illuminated （SI）, but not in those from darkadapted （DT） and dark-recovered （DRT） soybean leaves. However, the treatment did not cause such a decrease in amounts of the PsbS protein in the thylakoids from saturating light-illuminated wheat leaves. These results support the conclusion that saturating light illumination induces a reversible dissociation of some light-harvesting complex Ⅱ （LHClI） from PSII reaction center complex in soybean leaf but not in wheat leaf.

Artificial light-harvesting systems fabricated by supramolecular host–guest interactions

Artificial light-harvesting systems(LHSs) have drawn increasing research interest in recent times due to the energy crisis worldwide. Concurrently, macrocycle-based host–guest interactions have played an important role in the development of supramolecular chemistry. In recent years, studies towards artificial LHSs driven by macrocycle-based host–guest interactions are gradually being disclosed. In this mini-review, we briefly introduce the burgeoning progress of artificial LHSs driven by host–guest interactions. We believe that an increasing number of reports of artificial LHSs driven by host–guest interactions will appear in the near future and will provide a viable alternative for the future production of renewable energy.

An Artificial Light-Harvesting System with Tunable Fluorescence Color in Aqueous Sodium Dodecyl Sulfonate Micellar Systems for Photochemical Catalysis

Main observation and conclusion In the present work,an artificial light-harvesting system with fluorescence resonance energy transfer(FRET)is successfully fabricated in aqueous sodium dodecyl sulfonate(SDS)micellar systems.Since the tight and orderly arrangement of dodecyl in the SDS micelles is hydrophobic,tetra-(4-pyridylphenyl)ethylene(4PyTPE)can be easily encapsulated into the hydrophobic layer of SDS micelles through noncovalent interaction,which exhibits aggregation-induced emission(AIE)phenomenon and can be used as energy donor.By using amphoteric sulforhodamine 101(SR101)fluorescent dye attached to the negatively charged surface of SDS micelles through electrostatic interaction as energy acceptor,the light-harvesting FRET process can be efficiently simulated.Through the steady-state emission spectra analysis in the micelle-mediated energy transfer from 4PyTPE to SR101,the fluorescence emission can be tuned and white light emission with CIE coordinates of(0.31,0.29)can be successfully achieved by tuning the donor/acceptor ratio.More importantly,to better mimic natural photosynthesis,the SDS micelles with 4PyTPE and SR101 FRET system showed enhanced catalytic activity in photochemical catalysis for dehalogenation ofα-bromoacetophenone in aqueous solution and the photocatalytic reaction could be extended to gram levels.

Changes in Thermostability of Photosystem Ⅱ and Leaf Lipid Composition of Rice Mutant with Deficiency of Light-harvesting Chlorophyll a/b Protein Complexes

We studied the difference in thermostability of photosystem Ⅱ （PSII） and leaf lipid composition between a T-DNA insertion mutant rice （Oryza sativa L.） VG28 and its wild type Zhonghuau. Native green gel and SDS-PAGE electrophoreses revealed that the mutant VG28 lacked all light-harvesting chlorophyll a/b protein complexes. Both the mutant and wild type were sensitive to high temperatures, and the maximal efficiency of PSII photochemistry （FJ Fm） and oxygen-evolving activity of PSII in leaves significantly decreased with increasing temperature. However, the PSII activity of the mutant was markedly more sensitive to high temperatures than that of the wild type. Lipid composition analysis showed that the mutant had less phosphatidylglycerol and sulfoquinovosyl diacylglycerol compared with the wild type. Fatty acid analysis revealed that the mutant had an obvious decrease in the content of 16：1t and a marked increase in the content of 18：3 compared with the wild type. The effects of lipid composition and unsaturation of membrane lipids on the thermostability of PSII are discussed.